Impeller for centrifugal blowers or pumps



United States Patent() INIPELLER FOR CENTRIFUGAL BLOWERS R PUlVIPS Alfred Buchi, Hurden, Switzerland Application May 23, '1955, Serial No. 510,231 YClaims priority, application Switzerland June 3, 1954 6 claims. (Cl. 10s-115) The present invention relates to impellers for centrif ugal blowersv or pumps and more particularly to a cast impeller wheel wherein a hub part of light metal and carrying the disc and vanes is provided with a hub sleeve or box of a metal of higher rigidity.

The salient object of the invention is to prevent, in the casting of an impeller wheel'in a horizontal posi- 2,968,223 Ptented oct. 13, 1959 Reference is made to the attached drawings wherein embodiments of the invention are illustrated and in which tion, the occlusion of air between the material being cast and an undercut annular side of the hub sleeve or box.

A further object of the invention is to obtain a close adherence of the cast material about the hub sleeve or box with the material being clamped by peripheral annular extensions having undercut walls on the hub sleeve whereby the rigidity of the impeller in the radial and peripheral direction is strengthened materially by the hub sleeve or bo-x.

"ln the known embodiments of such wheels, the ends are achieved by projecting annular parts which are not provided with undercut sides. The annular sides lie in a plane normal to the axis, are directed outwardly at an angle in such a fashion that-in casting kabout the hub in the horizontal position, the air about the extensions is immediately displaced upwardly.' This is objectionable in that the material is frequently not secured to the extensionsV and in use, centrifugal forces detach the cast material yfrom the hub surface whereupon cracks may occur in the cast material ultimately resulting in the destruction of the impeller.v

The present invention provides .at least one of, the undercut ,sides of the extensions withradial notches or indentations which originate from the location where the undercut isA at armaximum andV outside are of a depth which at least corresponds to the degree of the undercut. To augment the ,clamping engagement of the cast material by the hub sleeve, it is advantageous to provide onl both sides of an extension embedded on all sides in cast material, radial notches. The notches of the two sides of-an extension Acan be arranged in mutually offset relation lso that the rigidity of `the'extensions is not weakened.

The impeller is cast in a fashion known per se with the vanes disposed at the bottom in the horizontal position, with the upper end of the hub lying at a higher level than the joined portion of the disc and at such location including a pouring inlet. In this regard, the greatest casting pressure is generated along the hub sleeve and at this Zone, the casting material is maintained liquid for the greatest length of time. Due to the fact that the casting material cools `and solidies from the outside, a close adherence of the material about the hub sleeve is effected. The boundary surface of the impeller disc remote from the vanes is constructed at least partly in the shape of a conical surface. At one area between the hubrsleeve or box and the outer periphery of the wheel, the conical boundary surface can be sub-divided by an axially protruding annular-shaped rib into two conical parts.

the same referencek characters denote corresponding parts in the several views.

Fig. l is a vertical sectional view of an impeller provided with radial vanes. and a cover disc arranged `thererupon in a ready cast state in the mold of a mold box.

Y Fig. 2 is a view similar to Fig. l of an impeller wheel of open radial construction.

Fig. 3 is a section taken along the line I-I of Fig. 1.

Fig. 4 is a sectional perspective view of the hub assembly.

Referring to Fig. 1, a centrifugal blower or pump impeller is denoted generally 1 and includes a disc 3, vanes 2, cover disc 4 with the disc 3 having a hub part 5. A hub sleeve A of high grade material is cast to the hub part 5, and, the periphery ofthe sleeve is provided with annular extensions 6e, 7 and 3. The disc 3 and thehub part 5 are of light metal and is cast into depressions 9 and 9 formed by the extensions 6, 7 and 8. Ity will be noted that the extensions are provided with undercut side walls a, a', b and c in such as fashion as to dene bayonetlike connections between the hub sleeve A and the hub part 5 at the location of their highest strains due to centrifugal and other forces during operation of the impeller.

The permissible stresses in the light metal part as a result of these aforementioned forces increase and the stretching compared with a wheel made entirely of light metal decrease. Hence, if the light metal part of the impeller was cast together with the hub sleeve without the use of the present invention, the increasing surface of the liquid casting `material would first contact the outer downwardly extending margins d throughout the entire periphery and the air between the undercut side walls and the material being occluded beneath the sides.

Such a drawback is overcome by the invention by the provision of notches k on the side remote from4 the pouring inlet so that during casting, the air can escape through the notches Akiupwardly above thelevel of the casting material and thus, the undercut areas between the extensions as well as the notches can be filled with thev casting material. Thel bases of the notches k originate vat the root of the? undercut sides or at vthe point of smallest axial thickness, namely the zone of maximum undercut of extensions 6 and 7. The notches k can extend with their bases more deeply into the extension in an outward direction so that the bases lie ina surface extending obliquely to the axis of vthe impeller with the inclination being directed upwardly toward the pouring inlet whereby a rigid connection between the hub part and the hub sleeve is eifected. To the same end, both side walls a and a" of the extension l7 may be fprovided with notches, and, the number 'of notches can be so selected as to provide a stronger connection between the light metal parts aud the hub sleeve A.

It will be noted from Figs. 1 and 2 that the casting material is admitted into the mold through a pouring inlet or -gate E, and, the air can escape through air vents or channels L1 and LZ.

With reference to Fig. 3, it can be seen that side a of the extension 7 includes six notches, and, for a more sturdy connection between the hub part 5 and the hub sleeve A, the side wall a may also be formed with notches k. The notches k are preferably odset peripherally respecting the notches k as indicated by the dotted lines in Fig. 3.

.By virtue of the invention, it is possible to cast the impeller in a horizontal position, namely withthe axis of rotation being vertically disposed whereby all casting elements lying in the same radial planes during the casting cycle are subject to the same casting pressure and have material of the same strength, rigidity and tension, in spite of the rotation resisting notches and the rigid connection with the hub sleeve. During operation, equal stresses occur in all of'these radial planes. Y

In impellers having cover discs on the vanes, it is also possible `to cast such wheels -in the horizontal position with the disc and vanes located at the bottom of the assembly.

The pouring inlet E and the` air vents L1 and L2 are arranged as shown in Figs. 1 and 2, and, at least one inlet is arranged in the area of the hub part 5 at the highest zone of the horizontally disposed form of the light metal componentsof the wheel. The air escape vents L1 and L2 have at least one surface level and above the vane and the cover disc. The upper area of the irnpeller mold or form is patterned to rise uniformally from the outside toward the inside (toward the pouring inlet and air escapevents) whereby the air is completely displaced by the castinlg material simultaneously upwardly, or in other words through the air'escape vents to the exterior of the casting form or mold. v

It is to be understood that changes and modifications of the invention can be made by one skilled in the art. provided such changes `or modiiications do not depart from the spirit and scope of the appended claims.

I claim: t

1. A cast impeller wheel for centrifugal blowers and the like comprising a hub part ending towards the outer periphery in a disc having a vane thereon with the hub part and vane being of light metal, a hub sleeve of a material of higher rigidity than the said light metal, `annular extensions in spaced relationship on .the periphery of the hub sleeve, said extensions having side walls between adjacent extensions defining several undercut and adjacent notched areas, the metal of the hub partextending into the undercut and notched areas and engaging the side walls of the extensions and the surfaces of the notched areas so that the material of the hub sleeve is firmly anchored to the hub part to resist centrifugal and circumferential forces during rotation of the wheel,

2. Aycast impeller wheel for centrifugal blowers and the like comprising a hub part having a vane thereon with the hub part and vane being of light metal, a hub sleeve of a material of higher rigidity than the light metal, -annular extensions on the periphery of the hub sleeve defining annular grooves with undercut side walls between adjacent extensions, and severalcircumferentally spaced Ysubstantially radial notches in the undercutside walls of said extensions, the metal of the hub part extending into thegrooves and engaging the undercut side walls and thenotchesq ;Y ,g 'g

'73. A cast impeller wheel as defined in claim l wherein tile hub part includes a disc which in part is of conical s ape. ,j I Q 4. A cast impeller wheel for centrifugal blowers and theflike Ycomprising a hub part having a vaneV thereon with the hub part and vane being of light metal, a hub sleeve of a material of higher rigidity than the light metal, annular extensions on the periphery of the hub sleeve defining annular grooves with undercut side walls between adjacent extensions, several circumferentially spaced substantially radial notches in the undercut side walls of said extensions, metal of the hub part extending into said grooves and engaging said undercut side Walls and said notches, and the notches originating at the area most deeply undercut and having exteriorly a depth of at least the degree'of the undercut;

5. A cast impeller wheel for centrifugal blowers and the like comprising a hub part ending towards the outer periphery in a disc having a vane thereon with the hub part and vane being of light metal,V `a hub sleeve of a material of higher rigidity than the said light metal, annular extensions in spaced relationship on the periphery of the hub sleeve, said extensions having side walls between adjacent extensions deiining several undercut and adjacent notched areas, the metal of the hub'part extending into the undercut and notched areas and engaging the side walls of the extensions and the surfaces of the notched areas so that the material of the hub sleeve is firmly anchored to the hub part to resist centrifugal and circumferential forces during rotation of the wheel, the notched areas being provided on both undercut side walls of an extension embedded on all sides 'in cast metal.

6. A cast impeller Wheel for centrifugal blowers and the like comprising ak hub part having aVvane thereon with the hub part and vane being of light metal, a hub sleeve of a material of higher rigidity than the light metal, annular extensions on the periphery of the hub sleeve defining annular grooves with undercut side walls between adjacent extensions, several circumferentially spaced substantially radial notches in the undercut side Walls of said extensions, metal of the hub partextending into said grooves and engaging said undercut side walls and said notches, the notches originating at the area most deeply undercut and having exteriorly a depth of at least the degree of the undercut, and the notches on one and the same extension being disposed peripherally in mu# tually offset relationship. Y f

References Cited in the file of this patent UNITED STATES PATENTS Germany Oct. 29, 1953 

